EP0848872B1 - Method and device for the sealing of computer data - Google Patents

Abstract

Digital data is provided with a time stamp of an internal time signal of an internal clock. The internal time signal is validated by receiving and evaluating an internal broadcast or a cable signal of an external time source, from which a standard time can be derived, comparing the standard time with the internal time signal of the internal clock, and time stamping the digital data. The digital data is time stamped only if a time difference between the internal and external time signals lies within a given tolerance range. Finally, the time-stamped digital data is encrypted.

Description

Electronic data and information exchange using computers, faxes, telex and other related media has seen tremendous growth in recent years receive. The growing use of EDP in all areas is in view the quality and quantity of the data processed before a completely new one Dimension of the required data security. This applies in particular to remote data transmission (DFÜ), as daily press reports show. Examples can be found in Ärzte-Zeitung 14, No. 86, May 11, 1995 "Internet is not suitable for sensitive data" and PraxisComputer No. 1, February 10, 1995, p. 15 "Don't trust anyone via fax ..."

The demand for data sealing, document authenticity and legally binding Communication is getting louder. It is a matter of time before the legislature does so Guidelines. The wording of a corresponding interview is in PraxisComputer No. 5, August 10, 1995, p. 36 "Making better use of scarce resources", interview with Dr. Winfried Schorre and Horst Seehofer, printed.

Some of the possible manipulation options are briefly listed below, to clarify the situation.

Example medicine

The surgeon created postoperatively by dictation, which was then written by the typist entered into the computer, the operation report. It turns up later out that the operator made a mistake, e.g. based on a previously diagnosed Lens opacification Removal of the eye lens, albeit on the wrong one Page. The surgeon subsequently tries the preoperative finding (Left lens clouding) manipulated (Right lens clouding) to relieve yourself.

Example finance

Transactions with an exchange rate at time t1 at time t2 is Falling course, subsequent manipulation is said to fraudulently result in loss prevent

Example research

Who first documented an invention?

Example legal system

Creation of minutes when taking evidence, when used in court, document authenticity is required.

Example data exchange

The discharge letter of a psychiatric patient should be sent to the family doctor via modem be sent. The authenticity of the recipient must be ensured and unauthorized Access to confidential documents can be prevented. See also in PraxisComputer No. 6, October 15, 1994, p. 5: "Confidentiality and data networks".

The Physikalisch Technische Bundesanstalt in Braunschweig sends them through a cesium clock time determined by means of radio waves from Mainflingen Within a radius of 1500 - 2000 km. More details under ELV-Journal 6/94, p.27 ff "DCF reception technology".

The receiver modules for radio clock signals have a high technical level (such as in Design & Elektronik 10, May 16, 1995, code 242 "Industrial clocks in the atomic age" explained in more detail) and deliver the complete date / time information every minute, in hereinafter referred to as normal time.

There are also time signal signals abroad, such as MSF (England) and WWVR (USA), the time signal is also in GPS (global positioning system, see below).

Since there is information, there has been a desire to encrypt it before to protect general access. The security of the key used correlates with the goodness of the key algorithm.

Various encryption methods are available to keep confidential data confidential available, which according to the effort a more or less great data security Offer. In principle, a distinction is made between symmetrical (crypto methods according to Feal, DES and others) and asymmetrical processes (RSA, PGP and others).

Various companies in the direction of document authenticity and legally binding Communication has so far not provided a satisfactory solution. Equality the digital signature with the handwritten signature is the subject of more intense Research as in c't Magazin 1995, number 6, p. 46 "Krypto-Enid" and in Design & Electronics 14/15, 07/18/95, code 212 "single-chip controller for crypto cards" executed. Compared to the sole encryption, the digital signature offers diverse advantages (Glade, A., Reimer, H., Struif, B .: digital signature and security-sensitive Applications, Wiesbaden 1995).

The subsequent manipulation of EDP data poses an as yet unsolved problem A file becomes a document in the legal sense only when it is printed out, which must be dated and signed. Given the wealth of data and the speed of their creation and destruction (data turnover) bumps this Processes to the limits of what is possible.

The growing exchange of data via computer, fax and other media as well as permanently increasing number of networks at national and international level (Internet and others, see also in Ärzte-Zeitung 14, No. 86, 11.05.95 "Internet is for sensitive Data not suitable ") require adequate data security measures in PraxisComputer No. 1, February 10, 1995, p. 15 "Don't trust anyone via fax ...." and c't Magazine 1994, Issue 8, p. 230 ff :: "Data locks, basics of cryptology") WO-A-92/03 000 discloses a system for time stamping a digital document. An author prepares a digital one Document and sends it to a in a first embodiment Authority (TSA) timestamp. There is the document timestamped, i.e. the document becomes digital data added that represent the time, and the institution adds nor their signature to, for example, the correctness or Document the authenticity of the time stamp. Then it will be with the time stamp and the signature on the document Author who sent proof of the Existence of the original document. To one This can prevent future manipulation of the document Document before sending to the TSA using, for example, a Hash function to be compressed, the hash compression instead of the document at the institution timestamped and is signed. A second embodiment differs from the first by using a network instead of the institution or a "world" used by writers who are mutually at random the time stamp and Issue signature on the documents sent. The Institution TSA or the author world uses the as time "Computer clock time", i.e. the manipulable internal clock of the computer dealing with time stamping.

The article by Davida et al .: "Arbitration in Tamper Proof Systems ", Advances in Cryptology-Crypto 87 Proceedings, Santa Barbara, CA, USA, 16-20. Aug. 1987, ISBN 3-540-18796-0, 1988, Berlin, West Germany, Springer Verlag, pages 216-222, describes various methods for generating Tamper-proof systems, such as digital Signature systems, systems with public keys and Notary systems that include time stamping. This is how one becomes Message encrypted using a device. Here, a message number mc and a in the device Time stamp ts attached to the message and encrypted. From the result, ie. the message plus the number mc plus that Time stamp ts, becomes an encrypted hash function ha generated. However, no statement is used about the Time hit.

A disadvantage of the above known methods and systems the fact that none of the procedures are a safe time can guarantee, so that a possibility of manipulation is not guaranteed with regard to the time used.

The invention is therefore based on the object of a method and a device for creating a time stamp or Sealing digital data, creating the for the Time stamping took a little time Has manipulation possibility.

The object is achieved by the features of method claims 1 and 2 and the device claims 11 and 12 solved. Preferred embodiments of the invention are the subject of Subclaims.

The method and the device described here cause access to the Sealed data is usually denied and thus represents an essential Step towards document authenticity and legally binding communication (see Fig. 1 data flow scheme).

For data transport, this means that the authenticity of the sender and receiver guaranteed and unauthorized access to the data sent by the simultaneous Encryption is prevented.

The method and the device for sealing computer data by means of a combination from normal time integration, authentication and encryption protects them sealed data from unauthorized access or manipulation, both in stationary IT area (exemplary embodiment PC plug-in card) as well as for remote data transmission (Example of additional board). See, Fig. 2: Device for data sealing.

At the PC level, a plug-in card is used for retrofitting, and one for the EDI devices Additional board favored. Of course, it is an attempt by technology to do this Miniaturize circuits and combine them in the smallest possible space. Depending on the quantity, a user-specific one can also be used, especially for new devices Implement IC (ASIC) solution. A coupling of the device according to the invention the PC (i.e. computer in general) can also be connected via any interface (serial, parallel, PCMCIA adapter).

3 shows the components of the device and the method

• Signalauswertung
• Signalüberprüfung
• Bereitstellung der Identifikationsnummer der Vorrichtung
• Verschlüsselung des empfangenen Signals
• Manipulationskontrolle

The device consists of electronic components, which have to fulfill the following tasks:

• Signal evaluation
• Signal check
• Providing the device identification number
• Encryption of the received signal
• Tamper control

Existing channels:

The transmitter provides the date and time information. In addition to the time signal transmitters other signal carriers such as satellite, TV cable, telephone, TV transmitter, etc. in question. So-called providers (e.g. Telekom) can also offer the option of Signal assignment or integration can be granted.

Specially designed transmitters

1 Bereitstellung der Normalzeit in verschlüsselter Form.

2. Variabilität des Sendezeitpunkts.

3 Durchmischung von echter und falscher Information.

4. Sender- Empfangersynchronisation mit begrenzter Gültigkeitsdauer.

5. Mischung der Information von 1 - 4.

6. Bidirektionales Signal zur Signalübermittlung.

A specially designed transmitter increases data security through the following factors:

1 Provision of standard time in encrypted form.

2. Variability of the time of transmission.

3 Mixing of real and false information.

4. Transmitter-receiver synchronization with a limited period of validity.

5. Mix the information from 1 - 4.

6. Bidirectional signal for signal transmission.

The nature of the receiver depends on that of the transmitter. In principle can Radio and cable signals are received. A corresponding logic evaluates the received ones Signals off.

The authenticity is checked for the radio clock signal due to a lack of specificity additional signals about the counting up of the time pulse, d. H. with any manipulation entries older than the date are the last queried, unadulterated date-time signal recognized as manipulation. In addition, the received signal with a internal clock (RTC, Real Time Clock) adjusted, with time differences outside of a control area indicate manipulation.

Authentication takes place via a device and / or a method that unequivocally determines the identity of the sender or the recipient of a message.
The electronic signature is currently the subject of research (see in Design & Electronics 14/15, 07/18/95, reference number 212 "single-chip controller for crypto cards"). Other devices and methods (card readers, fingerprint readers, and transponder systems as described in Design & Electronics, reference number 283 "Non-contact identification", etc.) are also suitable for proving authentication.

The time signal is modified using hardware (GAL, PAL and / or others Hardware encryption methods such as the Clipper chip, which was published in c't Magazin 1994, Issue 8, p. 24 "The NSA and the Clipper Chip" is explained) and / or using software (Encryption algorithm, e.g. according to the RSA procedure, more details in c't magazine 1994, Issue 8, pp. 230 ff: "Data Locks, Fundamentals of Cryptology". A decryption can only be done by the person who holds the key to the modification logic owns.

To prevent mechanical manipulation, the chip or the corresponding Components of the plug-in card cast in and with an electromechanical Coupling technology provided, so that a subsequent reading of microprocessor elements is difficult. 5, the contact has the Shielding 1 and 2 result in the deletion of the programmed components, so-called black box solution.

Data manipulation is done through parity checking and other mathematical and / or hardware test methods recognized. Security increases with the complexity of the Test method.

In America, independent data protection institutions have so-called "trust Center "set up to act as a trusted third party as an outside party To take data protection. This concerns encryption and decryption, the allocation and the storage of keys and the cooperation with providers and corresponding Notaries for the neutral authentication of communication keys, e.g. Further details can be found in Praxis Computer No. 2, March 10, 95, pp. 16/17; "With smart cards is much possible ".

In addition to identification (e.g. signature), a document contains the date and, if applicable, the time of the creation of the document. Via satellite positioning (GPS, global Positioning system), this location can be sufficiently identified and incorporated into the Include document in the same way as e.g. the normal time.

If the device is designed as a PC plug-in card, the radio clock signal takes over DCF 77 of the Physikalisch Technische Bundesanstalt in Braunschweig of the transmitter There are different versions of the receiver for time signals (size, Reception characteristics). The received signal is demodulated and amplified as a 100 ms or a 200 ms pulse per second to the PC plug-in card for evaluation passed on A microcontroller on the plug-in card sets the received signal pulses into a time information and saves using a special logic that is individual is tailored to each plug-in card, the last time received. The validation of the DCF-77 signal is shown in FIG. 7.

Each plug-in card is provided with an individual identification number. Hard and Software use this number for machine identification. The building blocks for the Receiving that need authentication and encryption, like the embodiment Plug-in card on the PC in Fig. 6 shows, not necessarily all on the card to be arranged yourself.

That from the original file using a signature process (e.g. MD5, Message Digest 5 signal generated by Ron Rivest, or similar) is provided with a header (information about those involved Sizes such as operating system version, file size, etc.) and with a defined part of the original file itself into a block, which in the present case has a size of 4kByte (so-called 4kBlock).

The microcontroller software accesses the time signal, installs it in the 4k block, encrypts it in the black box and attaches the time-stamped digital signature the original file. Optionally, this can also be saved separately or together with the original file can be encrypted again. (see Fig. 8).

Decryption can only be done by the key holder. Doing so Verification of subsequent manipulation carried out by the signature verification.

If the device according to the invention is designed as an additional card, then the corresponding Requirements for the transmitter and receiver for the implementation of the device as a PC plug-in card (so.).

In the field of data transmission, in addition to document authenticity, data backup also comes with Transport plays a crucial role Before sending the data is integrated the time signal is encrypted as described. Encryption and decryption are done through logic modules that correspond to the boundary conditions of the EDI devices must be integrated in the smallest space The encryption software is e.g. in the EPROM stored, the encryption hardware, for example, from a clipper chip consist.

In addition to the above Safety precautions create the time signal by setting of the time of sending and receiving true and false information further hurdles against unauthorized inspection and / or manipulation.

Fig. 1 ein Datenflußschema der Kommunikation einer versiegelten Datei zeigt,

Fig. 2 ein Schemabild einer erfindungsgemäßen Vorrichtung zur Datenversiegelung zeigt,

Fig. 3 die Komponenten der Vorrichtung nach Fig. 2 zeigt,

Fig. 4 mögliche Sender zur Distribution des verwendeten Zeitsignals zeigt,

Fig. 5 eine Schutzvorrichtung gegen unbefugtes Auslesen der programmierten Bauteile der erfindungsgemäßen Vorrichtung zeigt,

Fig. 6 ein Schemabild des erfindungsgemäßen Verfahrens zeigt, wobei die erfindungsgemäßen Vorrichtung als Einsteckkarte eines PCs realisiert ist,

Fig. 7 ein Blockdiagramm der Validierung eines externen Zeitsignals, beispielsweise eines DCF77 Signals, sowie der nachfolgenden Aktualisierung der Echtzeituhr zeigt,

Fig. 8 ein Blockdiagramm der Einbindung der Normalzeit beim Verschlüsseln zeigt, und

Fig. 9 ein Schemabild des Verfahrens und der Vorrichtung zur Versiegelung von Computerdaten zeigt.

A preferred embodiment is described below with reference to the accompanying drawings, in which

1 shows a data flow diagram of the communication of a sealed file,

2 shows a schematic image of a device for data sealing according to the invention,

3 shows the components of the device according to FIG. 2,

4 shows possible transmitters for distributing the time signal used,

5 shows a protective device against unauthorized reading of the programmed components of the device according to the invention,

6 shows a schematic diagram of the method according to the invention, the device according to the invention being implemented as a plug-in card of a PC,

7 shows a block diagram of the validation of an external time signal, for example a DCF77 signal, and the subsequent update of the real-time clock,

8 shows a block diagram of the incorporation of the normal time when encrypting, and

9 shows a schematic image of the method and the device for sealing computer data.

1 shows the data flow diagram of a file which is encrypted on the transmitter side and is decrypted on the receiver side, whereby to encrypt the data Signal is integrated, the normal time of an external source and an authentication code contains. For example, there is a file of the content abc on the transmitter side in a PC, fax, telex, cell phone or the like. This file can be over a transport level, for example remote data transmission (DFÜ) to the recipient side be transmitted. In this case, the content of the file can be manipulated. The receiving end includes the same components as the transmitter side, namely PC, fax, telex, Cell phone, or the like. To rule out subsequent manipulation of the file can and thus achieve document authenticity, the sender file the content abc undergo encryption, being validated in the encryption a normal time (external) and an identification is integrated. The one so encrypted A file with an illegible content is converted via the transport level to Transfer recipient. The transmitted, encrypted file is sent to the recipient decrypted by a key owner, with a manipulation check and an authentication check takes place. Then the file is in the readable again Form with the content abc before.

2 shows a diagram of possible embodiments of the device according to the invention for sealing computer data. In the case of stationary use the device, for example in a PC, a notebook or the like Device can be run in the form of a plug-in card if the stationary device is retrofitted In the case of a new device or original equipment, the invention Device by an integrated circuit, for example by a ASIC, the device according to the invention becomes non-stationary, i.e. in remote data transmission, for example in a fax, modem or the like, used, in the case of retrofitting this can be done, for example, with an additional board respectively. With a new device, the device becomes like in a stationary case by an integrated circuit, for example an ASIC.

3 shows a schematic structural diagram of the device according to the invention, consisting of the higher-level components receiver, authentication and Encoder.

The recipient receives date and time information. It is also possible to use a Location information, which can come from a GPS signal, for example, also This information is decoded, in the present embodiment a time signal decoder is given as an example for clarification. As a transmitter the date, time and / or location information comes already in the previous one listed sources, including a transmitter specially designed for this purpose into consideration.

The authentication establishes the identity of the sender or recipient of the message / file firmly. This can be done using a card reader, for example. Authentication can also by means of an identity process, such as an electronic signature.

The device can be encrypted using appropriate hardware, for example a clipper chip, or suitable software, d. H. a corresponding Encryption algorithm.

Fig. 4 shows an incomplete overview of possible transmitters of a suitable one Time signal. The necessary time signal can be transmitted by radio, for example as a DCF77 signal the Physikalisch Technische Bundesanstalt Braunschweig, or via satellite A transmission of the time signal via cable within a TV signal or telephone signal is also possible.

Fig. 5 shows a protective device against unauthorized reading or manipulation of programmed components of a device according to the invention. The so-called Blackbox solution comprises two protective grids designed as first and second shields, which surround the device according to the invention, the arranged on a circuit board electronic components and the shields cast in a potting compound are. Furthermore, an accumulator is arranged in the device, the potential of which the shields and the programmed components are connected so that a Contacting (short circuit) of the two shields with one another, for example deleting or Destruction of the connected components would result.

6 shows an embodiment of the method or device according to the invention as a plug-in card in a PC and the necessary functional parts A radio clock transmitter for example (Federal Republic of Germany) sends standard time as a DCF77 signal.

A suitable radio clock receiver converts these signals into a serial clock signal into the device according to the invention realized as a PC card. The PC plug-in card includes a microcontroller, an EPROM, an EEPROM, logic circuits, for example GALs, PALs, ASICs or the like, an encoder and a bus driver. Further an appropriate signature is entered via a card reader. By means of a Software and the plug-in card, the file of the content "abc" is encrypted in the PC, time stamped and signed so that the file to be transferred matches the encrypted content results.

FIG. 7 shows the validation of the received time signal in the microcontroller of FIG. 6. The receiver component supplies a DCF77 signal tocF to the microcontroller. The EEPROM of the device contains the last valid time signal t _E , whereby the condition t _DCF > t _E must be fulfilled. A real-time clock arranged in the device according to the invention, which can be implemented as an independent component or by means of the microcontroller, contains the current time t _A with a tolerance T, which can be, for example, 1 sec / month. The comparison t _DCF - t _A <| T (t _A - t _E ) | carried out. If the comparison is positive, the DCF77 signal is used for time stamping and the real time is updated

Fig. 8 shows schematically the inclusion of the normal time when encrypting. From one Original file "demo txt" is created using a signature process and with provide a header. With a defined part of the original file it becomes a so-called 4kByte block "4kblock.sta" generated. The microcontroller picks up in the black box the time signal DCF77 (or GPS) and performs the validation described in FIG. 7 of the DCF77 signal. The process is limited to n attempts. The validated Time signal is built into the 4kByte block and encrypted in the black box. The encrypted 4kByte block "4kblock.tst", i.e. the so-called time-stamped digital signature, is transferred to the original "demo.txt" file using software and the PC bus attached . Optionally, the combination of the original file "demo.txt" and the signature "4kblock.tst" saved separately or together again to a file "demo.tsc" be encrypted. Other inputs / outputs of the black box are motherboard activation, Chip card readers / writers and transponders.

9 shows an overall overview of the method and the device for sealing of computer data, both for "stationary" operation and for "dial-up" application. The normal time (and possibly further information) is determined by a time transmitter or cable, a transmission PC or transmission EDI, e.g. Fax machine, fed, who perform the coding / decoding of a corresponding information (file). The encrypted file is transmitted by means of remote data transmission (Dashed lines mean a coded dial-up signal). The respective sending PC or the sender fax, is over with a corresponding receiving PC or receiving fax a corresponding EDI path connected. The send / receive function can otherwise be reversed. Decoding, both on the transmitting and receiving side, archiving or printing out if authorization is available.

Claims (21)

1. A method of preparing a time stamp for digital data comprising the following steps:

   a) Receiving and evaluating an external broadcast or cable signal from an external time source from which the standard time t_DCF can be derived,

   b) Comparing the standard time t_DCF obtained in a) with an internal actual time signal t_A from an internal clock,

   c) Time-stamping the digital data if the difference between the internal and the external time signal is within a preset tolerance range,

   wherein the latest valid standard time signal t_E must satisfy the inequality tDCF > tE, and

   wherein the following inequality must apply for comparison of the actual external standard time t_DCF with the actual internal time t_A: tDCF - tA < |T * (tA - tE)|, wherein T denotes the tolerance of the internal clock.
2. A method of sealing digital data comprising the following steps:

   a) Receiving and evaluating an external broadcast or cable signal from an external time source from which the standard time t_DCF can be derived,

   b) Comparing the standard time t_DCF obtained in a) with an internal actual time signal tA from an internal clock,

   c) Time-stamping the digital data if the difference between the internal and the external time signal is within a preset tolerance range,

   wherein the latest valid standard time signal t_E must satisfy the inequality tDCF > tE, and

   wherein the following inequality must apply for comparison of the actual external standard time t_DCF with the actual internal time t_A: tDCF - tA < |T * (tA - tE)|, wherein T denotes the tolerance of the internal clock, and

   d) Coding the time-stamped digital data.
3. A method according to claim 2, characterised in that a signature for the digital data for time-stamping is obtained, the signature being time-stamped and subsequently coded.
4. A method according to any of the preceding claims, characterised in that the external broadcast or cable signal is the broadcast clock signal DCF77 of the Physikalisch-Technischen Bundesanstalt or the broadcast clock signal from another time transmitter.
5. A method according to any of claims 1 to 3, characterised in that the external broadcast or cable signal is from an independent transmitter, wherein the external broadcast or cable signal contains an authenticating code which sufficiently identifies the transmitter.
6. A method according to claim 5, characterised in that the external broadcast or cable signal is transmitted in coded form.
7. A method according to claim 5 or 6, characterised in that external broadcast or cable signal is transmitted or received at a time which itself is a part of the coding.
8. A method according to any of claims 5 - 7, characterised in that the external broadcast or cable signal contains true and false information.
9. A method according to any of the preceding claims, characterised in that the external broadcast or cable signal contains information from which the place of reception can be determined.
10. A method according to any of the preceding claims, characterised in that the external broadcast or cable signal is a GPS signal.
11. Apparatus for preparing a time stamp for digital data comprising:

    A receiver for receiving and evaluating an external broadcast or cable signal from an external time source from which the standard time t_DCF can be derived,

    An internal clock for generating an internal time signal t_A,

    A comparator for comparing the obtained external standard time t_DCF with the internal time t_A,

    A memory containing a latest valid standard time signal t_E and

    A means for time-stamping the digital data if the difference between the internal and the external standard time signal is within a preset tolerance range,

       wherein the latest valid standard-time signal t_E must satisfy the inequality tDCF > tE and    wherein the following inequality must apply for comparison of the actual external standard time t_DCF with the actual internal time t_A: tDCF - tA < |T * (tA - tE)|, wherein T denotes the tolerance of the internal clock.
12. Apparatus for sealing digital data comprising

    A receiver for receiving and evaluating an external broadcast or cable signal from an external time source from which the standard time t_DCF can be derived,

    An internal clock for generating an internal time signal t_A,

    A comparator for comparing the obtained external standard time t_DCF with the internal time t_A,

    A memory containing a latest valid standard time signal t_E and

    A means for time-stamping the digital data if the difference between the internal and the external standard time signal is within a preset tolerance range,

       wherein the latest valid standard-time signal t_E must satisfy the inequality tDCF > tE and    wherein the following inequality must apply for comparison of the actual external standard time t_DCF with the actual internal time t_A: tDCF - tA < |T * (tA - tE)|, wherein T denotes the tolerance of the internal clock,
    and
    a means for coding the time stamped digital data.
13. Apparatus according to claim 11 or 12,
    characterised in that after positive evaluation of the comparison, the latest valid time signal t_E in the form of the standard time t_DCF is stored in the memory and the internal real-time clock is updated.
14. Apparatus according to claim 12 or 13,
    characterised in that the apparatus comprises a means for preparing a signature for the digital data to be time stamped, wherein the signature is time-stamped and coded.
15. Apparatus according to any of claims 11 to 14,
    characterised in that the apparatus comprises an authenticating device.
16. Apparatus according to any of claims 11 to 15,
    characterised in that the apparatus has an identification number which is incorporated in the coding process.
17. Apparatus according to any of claims 11 to 16,
    characterised in that signal processing in the apparatus is performed by microprocessor components.
18. Apparatus according to any of claims 11 to 17,
    characterised in that the apparatus is protected against clocking-down.
19. Apparatus according to any of claims 11 to 18,
    characterised in that the apparatus is integrally cast with its components and is provided with an electromechanical coupling technique.
20. Apparatus according to any of claims 11 to 19,
    characterised in that the apparatus is disposed on a main computer circuit board or inside a means that can be used for remote data transmission.
21. Apparatus according to any of claims 11 to 19,
    characterised in that the apparatus is in the form of a PC plug-in card or additional circuit board.

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